Different retreats have different purposes, some will stay just a cool experience, some will improve your health, some will change your lifestyle and values completely. Some of them can be very relaxing, but I would rather go for the one that would require lots of inner work even may seem hard at some stage and learn as much as I can about myself about the world around me and how the level of concusses changes my reality. I think the best retreats gives you the tools that you implement into your life and make you a better version of yourself
here is a great article about levels of consciousness, this can give you a better understanding of what to look for at the retreats